using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Web;
using Examine;
using Examine.LuceneEngine.SearchCriteria;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Core;
using Umbraco.Core.Models;
using Umbraco.Core.Services;
using Umbraco.Web.Composing;

namespace Umbraco.Web
{
    using Examine = global::Examine;

    /// <summary>
    /// Provides extension methods for <c>IPublishedContent</c>.
    /// </summary>
    public static class PublishedContentExtensions
    {
        // see notes in PublishedElementExtensions
        //
        private static IPublishedValueFallback PublishedValueFallback => Current.PublishedValueFallback;

        #region Urls

        /// <summary>
        /// Gets the url for the content.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The url for the content.</returns>
        /// <remarks>Better use the <c>Url</c> property but that method is here to complement <c>UrlAbsolute()</c>.</remarks>
        public static string Url(this IPublishedContent content)
        {
            return content.Url;
        }

        /// <summary>
        /// Gets the absolute url for the content.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The absolute url for the content.</returns>
        public static string UrlAbsolute(this IPublishedContent content)
        {
            // adapted from PublishedContentBase.Url
            switch (content.ItemType)
            {
                case PublishedItemType.Content:
                    if (UmbracoContext.Current == null)
                        throw new InvalidOperationException("Cannot resolve a Url for a content item when UmbracoContext.Current is null.");
                    if (UmbracoContext.Current.UrlProvider == null)
                        throw new InvalidOperationException("Cannot resolve a Url for a content item when UmbracoContext.Current.UrlProvider is null.");
                    return UmbracoContext.Current.UrlProvider.GetUrl(content.Id, true);
                case PublishedItemType.Media:
                    throw new NotSupportedException("AbsoluteUrl is not supported for media types.");
                default:
                    throw new ArgumentOutOfRangeException();
            }
        }

        /// <summary>
        /// Gets the Url segment.
        /// </summary>
        /// <remarks>
        /// <para>Gets the url segment for the document, taking its content type and a specified
        /// culture in account. For invariant content types, the culture is ignored, else it is
        /// used to try and find the segment corresponding to the culture. May return null.</para>
        /// </remarks>
        public static string GetUrlSegment(this IPublishedContent content, string culture = null)
        {
            // for invariant content, return the invariant url segment
            if (!content.ContentType.VariesByCulture())
                return content.UrlSegment;

            // content.GetCulture(culture) will use the 'current' culture (via accessor) in case 'culture'
            // is null (meaning, 'current') - and can return 'null' if that culture is not published - and
            // will return 'null' if the content is variant and culture is invariant

            // else try and get the culture info
            // return the corresponding url segment, or null if none
            var cultureInfo = content.GetCulture(culture);
            return cultureInfo?.UrlSegment;
        }

        #endregion

        #region Template

        /// <summary>
        /// Returns the current template Alias
        /// </summary>
        /// <param name="content"></param>
        /// <returns></returns>
        public static string GetTemplateAlias(this IPublishedContent content)
        {
            var template = Current.Services.FileService.GetTemplate(content.TemplateId);
            return template == null ? string.Empty : template.Alias;
        }

        #endregion

        // fixme - .HasValue() and .Value() refactoring - in progress - see exceptions below

        #region HasValue

        /// <summary>
        /// Gets a value indicating whether the content has a value for a property identified by its alias.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="alias">The property alias.</param>
        /// <param name="recurse">A value indicating whether to navigate the tree upwards until a property with a value is found.</param>
        /// <returns>A value indicating whether the content has a value for the property identified by the alias.</returns>
        /// <remarks>Returns true if <c>GetProperty(alias, recurse)</c> is not <c>null</c> and <c>GetProperty(alias, recurse).HasValue</c> is <c>true</c>.</remarks>
        public static bool HasValue(this IPublishedContent content, string alias, bool recurse)
        {
            throw new NotImplementedException("WorkInProgress");

            //var prop = content.GetProperty(alias, recurse);
            //return prop != null && prop.HasValue();
        }

        /// <summary>
        /// Returns one of two strings depending on whether the content has a value for a property identified by its alias.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="alias">The property alias.</param>
        /// <param name="recurse">A value indicating whether to navigate the tree upwards until a property with a value is found.</param>
        /// <param name="valueIfTrue">The value to return if the content has a value for the property.</param>
        /// <param name="valueIfFalse">The value to return if the content has no value for the property.</param>
        /// <returns>Either <paramref name="valueIfTrue"/> or <paramref name="valueIfFalse"/> depending on whether the content
        /// has a value for the property identified by the alias.</returns>
        public static IHtmlString HasValue(this IPublishedContent content, string alias, bool recurse,
            string valueIfTrue, string valueIfFalse = null)
        {
            throw new NotImplementedException("WorkInProgress");

            //return content.HasValue(alias, recurse)
            //    ? new HtmlString(valueIfTrue)
            //    : new HtmlString(valueIfFalse ?? string.Empty);
        }

        #endregion

        #region Value
        
        /// <summary>
        /// Gets the value of a content's property identified by its alias, if it exists, otherwise a default value.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="alias">The property alias.</param>
        /// <param name="culture">The variation language.</param>
        /// <param name="segment">The variation segment.</param>
        /// <param name="defaultValue">The default value.</param>
        /// <param name="fallbackMethods">Options for fall-back if content not found.</param>
        /// <param name="visitedLanguages">A list of cultures already visited in looking for a value via a fall-back method.</param>
        /// <returns>The value of the content's property identified by the alias, if it exists, otherwise a default value.</returns>
        public static object Value(this IPublishedContent content, string alias, string culture = null, string segment = null, object defaultValue = default,
                                   int[] fallbackMethods = null, ICollection<int> visitedLanguages = null)
        {
            var property = content.GetProperty(alias);

            if (property != null && property.HasValue(culture, segment))
                return property.GetValue(culture, segment);

            return PublishedValueFallback.GetValue(content, alias, culture, segment, defaultValue, fallbackMethods, visitedLanguages ?? new List<int>());
        }

        #endregion

        #region Value<T>
        
        /// <summary>
        /// Gets the value of a content's property identified by its alias, converted to a specified type.
        /// </summary>
        /// <typeparam name="T">The target property type.</typeparam>
        /// <param name="content">The content.</param>
        /// <param name="alias">The property alias.</param>
        /// <param name="culture">The variation language.</param>
        /// <param name="segment">The variation segment.</param>
        /// <param name="defaultValue">The default value.</param>
        /// <param name="fallbackMethods">Options for fall-back if content not found.</param>
        /// <param name="visitedLanguages">A list of cultures already visited in looking for a value via a fall-back method.</param>
        /// <returns>The value of the content's property identified by the alias, converted to the specified type.</returns>
        /// <remarks>
        public static T Value<T>(this IPublishedContent content, string alias, string culture = null, string segment = null, T defaultValue = default,
                                 int[] fallbackMethods = null, ICollection<int> visitedLanguages = null)
        {
            var property = content.GetProperty(alias);

            if (property != null && property.HasValue(culture, segment))
                return property.Value<T>(culture, segment);

            return PublishedValueFallback.GetValue(content, alias, culture, segment, defaultValue, fallbackMethods, visitedLanguages ?? new List<int>());
        }

        // fixme - .Value() refactoring - in progress
        public static IHtmlString Value<T>(this IPublishedContent content, string aliases, Func<T, string> format, string alt = "",
                                           int[] fallbackMethods = null, ICollection<int> visitedLanguages = null)
        {
            var aliasesA = aliases.Split(',');
            if (aliasesA.Length == 0)
                return new HtmlString(string.Empty);

            throw new NotImplementedException("WorkInProgress");

            var property = content.GetProperty(aliasesA[0]);

            //var property = aliases.Split(',')
            //    .Where(x => string.IsNullOrWhiteSpace(x) == false)
            //    .Select(x => content.GetProperty(x.Trim(), recurse))
            //    .FirstOrDefault(x => x != null);

            //if (format == null) format = x => x.ToString();

            //return property != null
            //    ? new HtmlString(format(property.Value<T>()))
            //    : new HtmlString(alt);
        }

        #endregion

        #region Search

        public static IEnumerable<PublishedSearchResult> Search(this IPublishedContent content, string term, bool useWildCards = true, string indexName = null)
        {
            //TODO: we should pass in the IExamineManager?

            var searcher = string.IsNullOrEmpty(indexName)
                ? ExamineManager.Instance.GetSearcher(Constants.Examine.ExternalIndexer)
                : ExamineManager.Instance.GetSearcher(indexName);

            if (searcher == null)
                throw new InvalidOperationException("No searcher found for index " + indexName);

            var t = term.Escape().Value;
            if (useWildCards)
                t = term.MultipleCharacterWildcard().Value;

            var luceneQuery = "+__Path:(" + content.Path.Replace("-", "\\-") + "*) +" + t;
            var crit = searcher.CreateCriteria().RawQuery(luceneQuery);

            return content.Search(crit, searcher);
        }

        public static IEnumerable<PublishedSearchResult> SearchDescendants(this IPublishedContent content, string term, bool useWildCards = true, string indexName = null)
        {
            return content.Search(term, useWildCards, indexName);
        }

        public static IEnumerable<PublishedSearchResult> SearchChildren(this IPublishedContent content, string term, bool useWildCards = true, string indexName = null)
        {
            //TODO: we should pass in the IExamineManager?

            var searcher = string.IsNullOrEmpty(indexName)
                ? ExamineManager.Instance.GetSearcher(Constants.Examine.ExternalIndexer)
                : ExamineManager.Instance.GetSearcher(indexName);

            if (searcher == null)
                throw new InvalidOperationException("No searcher found for index " + indexName);

            var t = term.Escape().Value;
            if (useWildCards)
                t = term.MultipleCharacterWildcard().Value;

            var luceneQuery = "+parentID:" + content.Id + " +" + t;
            var crit = searcher.CreateCriteria().RawQuery(luceneQuery);

            return content.Search(crit, searcher);
        }

        public static IEnumerable<PublishedSearchResult> Search(this IPublishedContent content, Examine.SearchCriteria.ISearchCriteria criteria, Examine.ISearcher searchProvider = null)
        {
            //TODO: we should pass in the IExamineManager?

            var s = searchProvider ?? ExamineManager.Instance.GetSearcher(Constants.Examine.ExternalIndexer);

            var results = s.Search(criteria);
            return results.ToPublishedSearchResults(UmbracoContext.Current.ContentCache);
        }

        #endregion

        #region IsSomething: misc.

        /// <summary>
        /// Gets a value indicating whether the content is visible.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>A value indicating whether the content is visible.</returns>
        /// <remarks>A content is not visible if it has an umbracoNaviHide property with a value of "1". Otherwise,
        /// the content is visible.</remarks>
        public static bool IsVisible(this IPublishedContent content)
        {
            // note: would be better to ensure we have an IPropertyEditorValueConverter for booleans
            // and then treat the umbracoNaviHide property as a boolean - vs. the hard-coded "1".

            // rely on the property converter - will return default bool value, ie false, if property
            // is not defined, or has no value, else will return its value.
            return content.Value<bool>(Constants.Conventions.Content.NaviHide) == false;
        }

        /// <summary>
        /// Determines whether the specified content is a specified content type.
        /// </summary>
        /// <param name="content">The content to determine content type of.</param>
        /// <param name="docTypeAlias">The alias of the content type to test against.</param>
        /// <returns>True if the content is of the specified content type; otherwise false.</returns>
        public static bool IsDocumentType(this IPublishedContent content, string docTypeAlias)
        {
            return content.ContentType.Alias.InvariantEquals(docTypeAlias);
        }

        /// <summary>
        /// Determines whether the specified content is a specified content type or it's derived types.
        /// </summary>
        /// <param name="content">The content to determine content type of.</param>
        /// <param name="docTypeAlias">The alias of the content type to test against.</param>
        /// <param name="recursive">When true, recurses up the content type tree to check inheritance; when false just calls IsDocumentType(this IPublishedContent content, string docTypeAlias).</param>
        /// <returns>True if the content is of the specified content type or a derived content type; otherwise false.</returns>
        public static bool IsDocumentType(this IPublishedContent content, string docTypeAlias, bool recursive)
        {
            if (content.IsDocumentType(docTypeAlias))
                return true;

            return recursive && content.IsComposedOf(docTypeAlias);
        }

        public static bool IsNull(this IPublishedContent content, string alias, bool recurse)
        {
            return content.HasValue(alias, recurse) == false;
        }

        public static bool IsNull(this IPublishedContent content, string alias)
        {
            return content.HasValue(alias) == false;
        }

        #endregion

        #region IsSomething: equality

        public static bool IsEqual(this IPublishedContent content, IPublishedContent other)
        {
            return content.Id == other.Id;
        }

        public static HtmlString IsEqual(this IPublishedContent content, IPublishedContent other, string valueIfTrue)
        {
            return content.IsEqual(other, valueIfTrue, string.Empty);
        }

        public static HtmlString IsEqual(this IPublishedContent content, IPublishedContent other, string valueIfTrue, string valueIfFalse)
        {
            return new HtmlString(content.IsEqual(other) ? valueIfTrue : valueIfFalse);
        }

        public static bool IsNotEqual(this IPublishedContent content, IPublishedContent other)
        {
            return content.IsEqual(other) == false;
        }

        public static HtmlString IsNotEqual(this IPublishedContent content, IPublishedContent other, string valueIfTrue)
        {
            return content.IsNotEqual(other, valueIfTrue, string.Empty);
        }

        public static HtmlString IsNotEqual(this IPublishedContent content, IPublishedContent other, string valueIfTrue, string valueIfFalse)
        {
            return new HtmlString(content.IsNotEqual(other) ? valueIfTrue : valueIfFalse);
        }

        #endregion

        #region IsSomething: ancestors and descendants

        public static bool IsDescendant(this IPublishedContent content, IPublishedContent other)
        {
            return other.Level < content.Level && content.Path.InvariantStartsWith(other.Path);
        }

        public static HtmlString IsDescendant(this IPublishedContent content, IPublishedContent other, string valueIfTrue)
        {
            return content.IsDescendant(other, valueIfTrue, string.Empty);
        }

        public static HtmlString IsDescendant(this IPublishedContent content, IPublishedContent other, string valueIfTrue, string valueIfFalse)
        {
            return new HtmlString(content.IsDescendant(other) ? valueIfTrue : valueIfFalse);
        }

        public static bool IsDescendantOrSelf(this IPublishedContent content, IPublishedContent other)
        {
            return content.Path.InvariantStartsWith(other.Path);
        }

        public static HtmlString IsDescendantOrSelf(this IPublishedContent content, IPublishedContent other, string valueIfTrue)
        {
            return content.IsDescendantOrSelf(other, valueIfTrue, string.Empty);
        }

        public static HtmlString IsDescendantOrSelf(this IPublishedContent content, IPublishedContent other, string valueIfTrue, string valueIfFalse)
        {
            return new HtmlString(content.IsDescendantOrSelf(other) ? valueIfTrue : valueIfFalse);
        }

        public static bool IsAncestor(this IPublishedContent content, IPublishedContent other)
        {
            // avoid using Descendants(), or Ancestors(), they're expensive
            return content.Level < other.Level && other.Path.InvariantStartsWith(content.Path);
        }

        public static HtmlString IsAncestor(this IPublishedContent content, IPublishedContent other, string valueIfTrue)
        {
            return content.IsAncestor(other, valueIfTrue, string.Empty);
        }

        public static HtmlString IsAncestor(this IPublishedContent content, IPublishedContent other, string valueIfTrue, string valueIfFalse)
        {
            return new HtmlString(content.IsAncestor(other) ? valueIfTrue : valueIfFalse);
        }

        public static bool IsAncestorOrSelf(this IPublishedContent content, IPublishedContent other)
        {
            // avoid using DescendantsOrSelf() or AncestorsOrSelf(), they're expensive
            return other.Path.InvariantStartsWith(content.Path);
        }

        public static HtmlString IsAncestorOrSelf(this IPublishedContent content, IPublishedContent other, string valueIfTrue)
        {
            return content.IsAncestorOrSelf(other, valueIfTrue, string.Empty);
        }

        public static HtmlString IsAncestorOrSelf(this IPublishedContent content, IPublishedContent other, string valueIfTrue, string valueIfFalse)
        {
            return new HtmlString(content.IsAncestorOrSelf(other) ? valueIfTrue : valueIfFalse);
        }

        #endregion

        #region Axes: ancestors, ancestors-or-self

        // as per XPath 1.0 specs �2.2,
        // - the ancestor axis contains the ancestors of the context node; the ancestors of the context node consist
        //   of the parent of context node and the parent's parent and so on; thus, the ancestor axis will always
        //   include the root node, unless the context node is the root node.
        // - the ancestor-or-self axis contains the context node and the ancestors of the context node; thus,
        //   the ancestor axis will always include the root node.
        //
        // as per XPath 2.0 specs �3.2.1.1,
        // - the ancestor axis is defined as the transitive closure of the parent axis; it contains the ancestors
        //   of the context node (the parent, the parent of the parent, and so on) - The ancestor axis includes the
        //   root node of the tree in which the context node is found, unless the context node is the root node.
        // - the ancestor-or-self axis contains the context node and the ancestors of the context node; thus,
        //   the ancestor-or-self axis will always include the root node.
        //
        // the ancestor and ancestor-or-self axis are reverse axes ie they contain the context node or nodes that
        // are before the context node in document order.
        //
        // document order is defined by �2.4.1 as:
        // - the root node is the first node.
        // - every node occurs before all of its children and descendants.
        // - the relative order of siblings is the order in which they occur in the children property of their parent node.
        // - children and descendants occur before following siblings.

        /// <summary>
        /// Gets the ancestors of the content.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The ancestors of the content, in down-top order.</returns>
        /// <remarks>Does not consider the content itself.</remarks>
        public static IEnumerable<IPublishedContent> Ancestors(this IPublishedContent content)
        {
            return content.AncestorsOrSelf(false, null);
        }

        /// <summary>
        /// Gets the ancestors of the content, at a level lesser or equal to a specified level.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The ancestors of the content, at a level lesser or equal to the specified level, in down-top order.</returns>
        /// <remarks>Does not consider the content itself. Only content that are "high enough" in the tree are returned.</remarks>
        public static IEnumerable<IPublishedContent> Ancestors(this IPublishedContent content, int maxLevel)
        {
            return content.AncestorsOrSelf(false, n => n.Level <= maxLevel);
        }

        /// <summary>
        /// Gets the ancestors of the content, of a specified content type.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="contentTypeAlias">The content type.</param>
        /// <returns>The ancestors of the content, of the specified content type, in down-top order.</returns>
        /// <remarks>Does not consider the content itself. Returns all ancestors, of the specified content type.</remarks>
        public static IEnumerable<IPublishedContent> Ancestors(this IPublishedContent content, string contentTypeAlias)
        {
            return content.AncestorsOrSelf(false, n => n.ContentType.Alias == contentTypeAlias);
        }

        /// <summary>
        /// Gets the ancestors of the content, of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <returns>The ancestors of the content, of the specified content type, in down-top order.</returns>
        /// <remarks>Does not consider the content itself. Returns all ancestors, of the specified content type.</remarks>
        public static IEnumerable<T> Ancestors<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.Ancestors().OfType<T>();
        }

        /// <summary>
        /// Gets the ancestors of the content, at a level lesser or equal to a specified level, and of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The ancestors of the content, at a level lesser or equal to the specified level, and of the specified
        /// content type, in down-top order.</returns>
        /// <remarks>Does not consider the content itself. Only content that are "high enough" in the trees, and of the
        /// specified content type, are returned.</remarks>
        public static IEnumerable<T> Ancestors<T>(this IPublishedContent content, int maxLevel)
            where T : class, IPublishedContent
        {
            return content.Ancestors(maxLevel).OfType<T>();
        }

        /// <summary>
        /// Gets the content and its ancestors.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The content and its ancestors, in down-top order.</returns>
        public static IEnumerable<IPublishedContent> AncestorsOrSelf(this IPublishedContent content)
        {
            return content.AncestorsOrSelf(true, null);
        }

        /// <summary>
        /// Gets the content and its ancestors, at a level lesser or equal to a specified level.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The content and its ancestors, at a level lesser or equal to the specified level,
        /// in down-top order.</returns>
        /// <remarks>Only content that are "high enough" in the tree are returned. So it may or may not begin
        /// with the content itself, depending on its level.</remarks>
        public static IEnumerable<IPublishedContent> AncestorsOrSelf(this IPublishedContent content, int maxLevel)
        {
            return content.AncestorsOrSelf(true, n => n.Level <= maxLevel);
        }

        /// <summary>
        /// Gets the content and its ancestors, of a specified content type.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="contentTypeAlias">The content type.</param>
        /// <returns>The content and its ancestors, of the specified content type, in down-top order.</returns>
        /// <remarks>May or may not begin with the content itself, depending on its content type.</remarks>
        public static IEnumerable<IPublishedContent> AncestorsOrSelf(this IPublishedContent content, string contentTypeAlias)
        {
            return content.AncestorsOrSelf(true, n => n.ContentType.Alias == contentTypeAlias);
        }

        /// <summary>
        /// Gets the content and its ancestors, of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <returns>The content and its ancestors, of the specified content type, in down-top order.</returns>
        /// <remarks>May or may not begin with the content itself, depending on its content type.</remarks>
        public static IEnumerable<T> AncestorsOrSelf<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.AncestorsOrSelf().OfType<T>();
        }

        /// <summary>
        /// Gets the content and its ancestor, at a lever lesser or equal to a specified level, and of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The content and its ancestors, at a level lesser or equal to the specified level, and of the specified
        /// content type, in down-top order.</returns>
        /// <remarks>May or may not begin with the content itself, depending on its level and content type.</remarks>
        public static IEnumerable<T> AncestorsOrSelf<T>(this IPublishedContent content, int maxLevel)
            where T : class, IPublishedContent
        {
            return content.AncestorsOrSelf(maxLevel).OfType<T>();
        }

        /// <summary>
        /// Gets the ancestor of the content, ie its parent.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The ancestor of the content.</returns>
        /// <remarks>This method is here for consistency purposes but does not make much sense.</remarks>
        public static IPublishedContent Ancestor(this IPublishedContent content)
        {
            return content.Parent;
        }

        /// <summary>
        /// Gets the nearest ancestor of the content, at a lever lesser or equal to a specified level.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The nearest (in down-top order) ancestor of the content, at a level lesser or equal to the specified level.</returns>
        /// <remarks>Does not consider the content itself. May return <c>null</c>.</remarks>
        public static IPublishedContent Ancestor(this IPublishedContent content, int maxLevel)
        {
            return content.EnumerateAncestors(false).FirstOrDefault(x => x.Level <= maxLevel);
        }

        /// <summary>
        /// Gets the nearest ancestor of the content, of a specified content type.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="contentTypeAlias">The content type alias.</param>
        /// <returns>The nearest (in down-top order) ancestor of the content, of the specified content type.</returns>
        /// <remarks>Does not consider the content itself. May return <c>null</c>.</remarks>
        public static IPublishedContent Ancestor(this IPublishedContent content, string contentTypeAlias)
        {
            return content.EnumerateAncestors(false).FirstOrDefault(x => x.ContentType.Alias == contentTypeAlias);
        }

        /// <summary>
        /// Gets the nearest ancestor of the content, of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <returns>The nearest (in down-top order) ancestor of the content, of the specified content type.</returns>
        /// <remarks>Does not consider the content itself. May return <c>null</c>.</remarks>
        public static T Ancestor<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.Ancestors<T>().FirstOrDefault();
        }

        /// <summary>
        /// Gets the nearest ancestor of the content, at the specified level and of the specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The ancestor of the content, at the specified level and of the specified content type.</returns>
        /// <remarks>Does not consider the content itself. If the ancestor at the specified level is
        /// not of the specified type, returns <c>null</c>.</remarks>
        public static T Ancestor<T>(this IPublishedContent content, int maxLevel)
            where T : class, IPublishedContent
        {
            return content.Ancestors<T>(maxLevel).FirstOrDefault();
        }

        /// <summary>
        /// Gets the content or its nearest ancestor.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The content.</returns>
        /// <remarks>This method is here for consistency purposes but does not make much sense.</remarks>
        public static IPublishedContent AncestorOrSelf(this IPublishedContent content)
        {
            return content;
        }

        /// <summary>
        /// Gets the content or its nearest ancestor, at a lever lesser or equal to a specified level.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns>The content or its nearest (in down-top order) ancestor, at a level lesser or equal to the specified level.</returns>
        /// <remarks>May or may not return the content itself depending on its level. May return <c>null</c>.</remarks>
        public static IPublishedContent AncestorOrSelf(this IPublishedContent content, int maxLevel)
        {
            return content.EnumerateAncestors(true).FirstOrDefault(x => x.Level <= maxLevel);
        }

        /// <summary>
        /// Gets the content or its nearest ancestor, of a specified content type.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="contentTypeAlias">The content type.</param>
        /// <returns>The content or its nearest (in down-top order) ancestor, of the specified content type.</returns>
        /// <remarks>May or may not return the content itself depending on its content type. May return <c>null</c>.</remarks>
        public static IPublishedContent AncestorOrSelf(this IPublishedContent content, string contentTypeAlias)
        {
            return content.EnumerateAncestors(true).FirstOrDefault(x => x.ContentType.Alias == contentTypeAlias);
        }

        /// <summary>
        /// Gets the content or its nearest ancestor, of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <returns>The content or its nearest (in down-top order) ancestor, of the specified content type.</returns>
        /// <remarks>May or may not return the content itself depending on its content type. May return <c>null</c>.</remarks>
        public static T AncestorOrSelf<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.AncestorsOrSelf<T>().FirstOrDefault();
        }

        /// <summary>
        /// Gets the content or its nearest ancestor, at a lever lesser or equal to a specified level, and of a specified content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <param name="maxLevel">The level.</param>
        /// <returns></returns>
        public static T AncestorOrSelf<T>(this IPublishedContent content, int maxLevel)
            where T : class, IPublishedContent
        {
            return content.AncestorsOrSelf<T>(maxLevel).FirstOrDefault();
        }

        public static IEnumerable<IPublishedContent> AncestorsOrSelf(this IPublishedContent content, bool orSelf, Func<IPublishedContent, bool> func)
        {
            var ancestorsOrSelf = content.EnumerateAncestors(orSelf);
            return func == null ? ancestorsOrSelf : ancestorsOrSelf.Where(func);
        }

        /// <summary>
        /// Enumerates ancestors of the content, bottom-up.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="orSelf">Indicates whether the content should be included.</param>
        /// <returns>Enumerates bottom-up ie walking up the tree (parent, grand-parent, etc).</returns>
        internal static IEnumerable<IPublishedContent> EnumerateAncestors(this IPublishedContent content, bool orSelf)
        {
            if (content == null) throw new ArgumentNullException(nameof(content));
            if (orSelf) yield return content;
            while ((content = content.Parent) != null)
                yield return content;
        }

        #endregion

        #region Axes: descendants, descendants-or-self

        /// <summary>
        /// Returns all DescendantsOrSelf of all content referenced
        /// </summary>
        /// <param name="parentNodes"></param>
        /// <param name="docTypeAlias"></param>
        /// <returns></returns>
        /// <remarks>
        /// This can be useful in order to return all nodes in an entire site by a type when combined with TypedContentAtRoot
        /// </remarks>
        public static IEnumerable<IPublishedContent> DescendantsOrSelf(this IEnumerable<IPublishedContent> parentNodes, string docTypeAlias)
        {
            return parentNodes.SelectMany(x => x.DescendantsOrSelf(docTypeAlias));
        }

        /// <summary>
        /// Returns all DescendantsOrSelf of all content referenced
        /// </summary>
        /// <param name="parentNodes"></param>
        /// <returns></returns>
        /// <remarks>
        /// This can be useful in order to return all nodes in an entire site by a type when combined with TypedContentAtRoot
        /// </remarks>
        public static IEnumerable<T> DescendantsOrSelf<T>(this IEnumerable<IPublishedContent> parentNodes)
            where T : class, IPublishedContent
        {
            return parentNodes.SelectMany(x => x.DescendantsOrSelf<T>());
        }


        // as per XPath 1.0 specs �2.2,
        // - the descendant axis contains the descendants of the context node; a descendant is a child or a child of a child and so on; thus
        //   the descendant axis never contains attribute or namespace nodes.
        // - the descendant-or-self axis contains the context node and the descendants of the context node.
        //
        // as per XPath 2.0 specs �3.2.1.1,
        // - the descendant axis is defined as the transitive closure of the child axis; it contains the descendants of the context node (the
        //   children, the children of the children, and so on).
        // - the descendant-or-self axis contains the context node and the descendants of the context node.
        //
        // the descendant and descendant-or-self axis are forward axes ie they contain the context node or nodes that are after the context
        // node in document order.
        //
        // document order is defined by �2.4.1 as:
        // - the root node is the first node.
        // - every node occurs before all of its children and descendants.
        // - the relative order of siblings is the order in which they occur in the children property of their parent node.
        // - children and descendants occur before following siblings.

        public static IEnumerable<IPublishedContent> Descendants(this IPublishedContent content)
        {
            return content.DescendantsOrSelf(false, null);
        }

        public static IEnumerable<IPublishedContent> Descendants(this IPublishedContent content, int level)
        {
            return content.DescendantsOrSelf(false, p => p.Level >= level);
        }

        public static IEnumerable<IPublishedContent> Descendants(this IPublishedContent content, string contentTypeAlias)
        {
            return content.DescendantsOrSelf(false, p => p.ContentType.Alias == contentTypeAlias);
        }

        public static IEnumerable<T> Descendants<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.Descendants().OfType<T>();
        }

        public static IEnumerable<T> Descendants<T>(this IPublishedContent content, int level)
            where T : class, IPublishedContent
        {
            return content.Descendants(level).OfType<T>();
        }

        public static IEnumerable<IPublishedContent> DescendantsOrSelf(this IPublishedContent content)
        {
            return content.DescendantsOrSelf(true, null);
        }

        public static IEnumerable<IPublishedContent> DescendantsOrSelf(this IPublishedContent content, int level)
        {
            return content.DescendantsOrSelf(true, p => p.Level >= level);
        }

        public static IEnumerable<IPublishedContent> DescendantsOrSelf(this IPublishedContent content, string contentTypeAlias)
        {
            return content.DescendantsOrSelf(true, p => p.ContentType.Alias == contentTypeAlias);
        }

        public static IEnumerable<T> DescendantsOrSelf<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.DescendantsOrSelf().OfType<T>();
        }

        public static IEnumerable<T> DescendantsOrSelf<T>(this IPublishedContent content, int level)
            where T : class, IPublishedContent
        {
            return content.DescendantsOrSelf(level).OfType<T>();
        }

        public static IPublishedContent Descendant(this IPublishedContent content)
        {
            return content.Children.FirstOrDefault();
        }

        public static IPublishedContent Descendant(this IPublishedContent content, int level)
        {
            return content.EnumerateDescendants(false).FirstOrDefault(x => x.Level == level);
        }

        public static IPublishedContent Descendant(this IPublishedContent content, string contentTypeAlias)
        {
            return content.EnumerateDescendants(false).FirstOrDefault(x => x.ContentType.Alias == contentTypeAlias);
        }

        public static T Descendant<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.EnumerateDescendants(false).FirstOrDefault(x => x is T) as T;
        }

        public static T Descendant<T>(this IPublishedContent content, int level)
            where T : class, IPublishedContent
        {
            return content.Descendant(level) as T;
        }

        public static IPublishedContent DescendantOrSelf(this IPublishedContent content)
        {
            return content;
        }

        public static IPublishedContent DescendantOrSelf(this IPublishedContent content, int level)
        {
            return content.EnumerateDescendants(true).FirstOrDefault(x => x.Level == level);
        }

        public static IPublishedContent DescendantOrSelf(this IPublishedContent content, string contentTypeAlias)
        {
            return content.EnumerateDescendants(true).FirstOrDefault(x => x.ContentType.Alias == contentTypeAlias);
        }

        public static T DescendantOrSelf<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.EnumerateDescendants(true).FirstOrDefault(x => x is T) as T;
        }

        public static T DescendantOrSelf<T>(this IPublishedContent content, int level)
            where T : class, IPublishedContent
        {
            return content.DescendantOrSelf(level) as T;
        }

        internal static IEnumerable<IPublishedContent> DescendantsOrSelf(this IPublishedContent content, bool orSelf, Func<IPublishedContent, bool> func)
        {
            return content.EnumerateDescendants(orSelf).Where(x => func == null || func(x));
        }

        internal static IEnumerable<IPublishedContent> EnumerateDescendants(this IPublishedContent content, bool orSelf)
        {
            if (content == null) throw new ArgumentNullException(nameof(content));
            if (orSelf) yield return content;

            foreach (var desc in content.Children.SelectMany(x => x.EnumerateDescendants()))
                yield return desc;
        }

        internal static IEnumerable<IPublishedContent> EnumerateDescendants(this IPublishedContent content)
        {
            yield return content;

            foreach (var desc in content.Children.SelectMany(x => x.EnumerateDescendants()))
                yield return desc;
        }

        #endregion

        #region Axes: following-sibling, preceding-sibling, following, preceding + pseudo-axes up, down, next, previous

        // up pseudo-axe ~ ancestors
        // bogus, kept for backward compatibility but we should get rid of it
        // better use ancestors

        public static IPublishedContent Up(this IPublishedContent content)
        {
            return content.Parent;
        }

        public static IPublishedContent Up(this IPublishedContent content, int number)
        {
            if (number < 0)
                throw new ArgumentOutOfRangeException(nameof(number), "Must be greater than, or equal to, zero.");
            return number == 0 ? content : content.EnumerateAncestors(false).Skip(number).FirstOrDefault();
        }

        public static IPublishedContent Up(this IPublishedContent content, string contentTypeAlias)
        {
            return string.IsNullOrEmpty(contentTypeAlias)
                ? content.Parent
                : content.Ancestor(contentTypeAlias);
        }

        // down pseudo-axe ~ children (not descendants)
        // bogus, kept for backward compatibility but we should get rid of it
        // better use descendants

        public static IPublishedContent Down(this IPublishedContent content)
        {
            return content.Children.FirstOrDefault();
        }

        public static IPublishedContent Down(this IPublishedContent content, int number)
        {
            if (number < 0)
                throw new ArgumentOutOfRangeException(nameof(number), "Must be greater than, or equal to, zero.");
            if (number == 0) return content;

            content = content.Children.FirstOrDefault();
            while (content != null && --number > 0)
                content = content.Children.FirstOrDefault();

            return content;
        }

        public static IPublishedContent Down(this IPublishedContent content, string contentTypeAlias)
        {
            if (string.IsNullOrEmpty(contentTypeAlias))
                return content.Children.FirstOrDefault();

            // note: this is what legacy did, but with a broken Descendant
            // so fixing Descendant will change how it works...
            return content.Descendant(contentTypeAlias);
        }

        #endregion

        #region Axes: parent

        // Parent is native

        /// <summary>
        /// Gets the parent of the content, of a given content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <returns>The parent of content, of the given content type, else null.</returns>
        public static T Parent<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            if (content == null) throw new ArgumentNullException(nameof(content));
            return content.Parent as T;
        }

        #endregion

        #region Axes: children

        /// <summary>
        /// Gets the children of the content.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The children of the content.</returns>
        /// <remarks>
        /// <para>Children are sorted by their sortOrder.</para>
        /// <para>This method exists for consistency, it is the same as calling content.Children as a property.</para>
        /// </remarks>
        public static IEnumerable<IPublishedContent> Children(this IPublishedContent content)
        {
            if (content == null) throw new ArgumentNullException(nameof(content));
            return content.Children;
        }

        /// <summary>
        /// Gets the children of the content, filtered by a predicate.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="predicate">The predicate.</param>
        /// <returns>The children of the content, filtered by the predicate.</returns>
        /// <remarks>
        /// <para>Children are sorted by their sortOrder.</para>
        /// </remarks>
        public static IEnumerable<IPublishedContent> Children(this IPublishedContent content, Func<IPublishedContent, bool> predicate)
        {
            return content.Children().Where(predicate);
        }

        /// <summary>
        /// Gets the children of the content, of any of the specified types.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="alias">One or more content type alias.</param>
        /// <returns>The children of the content, of any of the specified types.</returns>
        public static IEnumerable<IPublishedContent> Children(this IPublishedContent content, params string[] alias)
        {
            return content.Children(x => alias.InvariantContains(x.ContentType.Alias));
        }

        /// <summary>
        /// Gets the children of the content, of a given content type.
        /// </summary>
        /// <typeparam name="T">The content type.</typeparam>
        /// <param name="content">The content.</param>
        /// <returns>The children of content, of the given content type.</returns>
        /// <remarks>
        /// <para>Children are sorted by their sortOrder.</para>
        /// </remarks>
        public static IEnumerable<T> Children<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.Children().OfType<T>();
        }

        public static IPublishedContent FirstChild(this IPublishedContent content)
        {
            return content.Children().FirstOrDefault();
        }

        /// <summary>
        /// Gets the first child of the content, of a given content type.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="alias">The content type alias.</param>
        /// <returns>The first child of content, of the given content type.</returns>
        public static IPublishedContent FirstChild(this IPublishedContent content, string alias)
        {
            return content.Children(alias).FirstOrDefault();
        }

        public static IPublishedContent FirstChild(this IPublishedContent content, Func<IPublishedContent, bool> predicate)
        {
            return content.Children(predicate).FirstOrDefault();
        }

        public static T FirstChild<T>(this IPublishedContent content)
            where T : class, IPublishedContent
        {
            return content.Children<T>().FirstOrDefault();
        }

        public static T FirstChild<T>(this IPublishedContent content, Func<T, bool> predicate)
            where T : class, IPublishedContent
        {
            return content.Children<T>().FirstOrDefault(predicate);
        }

        /// <summary>
        /// Gets the children of the content in a DataTable.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="services">A service context.</param>
        /// <param name="contentTypeAliasFilter">An optional content type alias.</param>
        /// <returns>The children of the content.</returns>
        public static DataTable ChildrenAsTable(this IPublishedContent content, ServiceContext services, string contentTypeAliasFilter = "")
        {
            return GenerateDataTable(content, services, contentTypeAliasFilter);
        }

        /// <summary>
        /// Gets the children of the content in a DataTable.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <param name="services">A service context.</param>
        /// <param name="contentTypeAliasFilter">An optional content type alias.</param>
        /// <returns>The children of the content.</returns>
        private static DataTable GenerateDataTable(IPublishedContent content, ServiceContext services, string contentTypeAliasFilter = "")
        {
            var firstNode = contentTypeAliasFilter.IsNullOrWhiteSpace()
                                ? content.Children.Any()
                                    ? content.Children.ElementAt(0)
                                    : null
                                : content.Children.FirstOrDefault(x => x.ContentType.Alias == contentTypeAliasFilter);
            if (firstNode == null)
                return new DataTable(); //no children found

            //use new utility class to create table so that we don't have to maintain code in many places, just one
            var dt = Core.DataTableExtensions.GenerateDataTable(
                //pass in the alias of the first child node since this is the node type we're rendering headers for
                firstNode.ContentType.Alias,
                //pass in the callback to extract the Dictionary<string, string> of all defined aliases to their names
                alias => GetPropertyAliasesAndNames(services, alias),
                //pass in a callback to populate the datatable, yup its a bit ugly but it's already legacy and we just want to maintain code in one place.
                () =>
                {
                    //create all row data
                    var tableData = Core.DataTableExtensions.CreateTableData();
                    //loop through each child and create row data for it
                    foreach (var n in content.Children.OrderBy(x => x.SortOrder))
                    {
                        if (contentTypeAliasFilter.IsNullOrWhiteSpace() == false)
                        {
                            if (n.ContentType.Alias != contentTypeAliasFilter)
                                continue; //skip this one, it doesn't match the filter
                        }

                        var standardVals = new Dictionary<string, object>
                            {
                                    { "Id", n.Id },
                                    { "NodeName", n.Name },
                                    { "NodeTypeAlias", n.ContentType.Alias },
                                    { "CreateDate", n.CreateDate },
                                    { "UpdateDate", n.UpdateDate },
                                    { "CreatorName", n.CreatorName },
                                    { "WriterName", n.WriterName },
                                    { "Url", n.Url }
                                };

                        var userVals = new Dictionary<string, object>();
                        foreach (var p in from IPublishedProperty p in n.Properties where p.GetSourceValue() != null select p)
                        {
                            // probably want the "object value" of the property here...
                            userVals[p.Alias] = p.GetValue();
                        }
                        //add the row data
                        Core.DataTableExtensions.AddRowData(tableData, standardVals, userVals);
                    }
                    return tableData;
                }
                );
            return dt;
        }

        #endregion

        #region Axes: custom

        /// <summary>
        /// Gets the root content for this content.
        /// </summary>
        /// <param name="content">The content.</param>
        /// <returns>The 'site' content ie AncestorOrSelf(1).</returns>
        public static IPublishedContent Root(this IPublishedContent content)
        {
            return content.AncestorOrSelf(1);
        }

        #endregion

        #region PropertyAliasesAndNames

        private static Func<ServiceContext, string, Dictionary<string, string>> _getPropertyAliasesAndNames;

        /// <summary>
        /// This is used only for unit tests to set the delegate to look up aliases/names dictionary of a content type
        /// </summary>
        internal static Func<ServiceContext, string, Dictionary<string, string>> GetPropertyAliasesAndNames
        {
            get => _getPropertyAliasesAndNames ?? GetAliasesAndNames;
            set => _getPropertyAliasesAndNames = value;
        }

        private static Dictionary<string, string> GetAliasesAndNames(ServiceContext services, string alias)
        {
            var type = services.ContentTypeService.Get(alias)
                ?? services.MediaTypeService.Get(alias)
                ?? (IContentTypeBase)services.MemberTypeService.Get(alias);
            var fields = GetAliasesAndNames(type);

            // ensure the standard fields are there
            var stdFields = new Dictionary<string, string>
            {
                {"Id", "Id"},
                {"NodeName", "NodeName"},
                {"NodeTypeAlias", "NodeTypeAlias"},
                {"CreateDate", "CreateDate"},
                {"UpdateDate", "UpdateDate"},
                {"CreatorName", "CreatorName"},
                {"WriterName", "WriterName"},
                {"Url", "Url"}
            };

            foreach (var field in stdFields.Where(x => fields.ContainsKey(x.Key) == false))
            {
                fields[field.Key] = field.Value;
            }

            return fields;
        }

        private static Dictionary<string, string> GetAliasesAndNames(IContentTypeBase contentType)
        {
            return contentType.PropertyTypes.ToDictionary(x => x.Alias, x => x.Name);
        }

        #endregion
    }
}